1. Field of the Invention
This invention generally relates to amplifiers, and more specifically, to a low-voltage, low-power, and low-noise amplifier.
2. Description of Related Art
As consumers are getting more concerned about vehicle driving safety, in addition to antilock brake system (ABS) and air bags of vehicles, a vehicle anti-crash safety system would further enhance driving safety. Millimeter wave radar system is becoming an important technology of vehicle anti-crash safety system, and short-range radar sensor employed in the millimeter wave radar system consists of a transmitter and a receiver. A low-noise amplifier (LNA) is a part of the receiver of the short-range radar sensor. The low-noise amplifier, as a part of the receiver, amplifies received signals and suppresses noises caused by the receiver itself. Therefore, how to design low-noise amplifiers has become an urgent issue.
Wireless communication technology has been rapidly developed, and the production cost of radio frequency (RF) wireless integrated circuit is becoming lower. General prior RF integrated circuits using specific fabrication processes, such as GaAs HEMT and SiGe HBT, not only have high cost, but also are unable to integrate with digital circuits, making system on chip (SOC) infeasible. Therefore, in order to lower production cost as well as integrate both digital circuits and analog circuits, employing designs of low cost CMOS (complementary metal-oxide semiconductor) process has become a trend of future integrated circuit design.
According to “High frequency LNA design in standard CMOS process” (IEEE Circuits Syst, pp. 5-8, June 2006, M. Egels, J. Gaubert, and P. Pannier), a low-noise amplifier designed by employing CMOS 0.13 process and operated at K-band is disclosed, the architecture of this low-noise amplifier consists of a common-source amplifier and a cascade amplifier. Compared with a traditional low-noise amplifier that consists of cascade amplifier only, this low-noise amplifier has much lower noise (NF=3.1 dB).
According to “26-42 GHz SOI CMOS low-noise amplifier” (IEEE J. Solid-State Circuit, vol. 39, no. 3, pp. 522-528, March 2004, F. Ellinger), a 26-42 GHz low-noise amplifier designed by employing 90 nm SOI CMOS process is disclosed, this low-noise amplifier consists of one cascade amplifier, its noise factor is NF=3.6 dB, but its power consumption is too high (40.8 mW). Also, the SOI process has higher production cost due to an isolation layer to separate active components from substrate in order to reduce power consumption.
According to “A 26 GHz low-noise amplifier in 0.18 μm CMOS technology” (IEEE Int. Symp. Electron Dev., pp. 93-98, November 2003, K. W. Yu et al), a 26 GHz low-noise amplifier designed by employing 0.18 μm CMOS process is disclosed, its architecture consists of three common-source amplifiers that are arranged in a cascade manner; and transistor is used for bias. However, this kind of bias will lower the linearity of amplifier. Since a standard CMOS process is used, of which the substrate has low resistance, signals are likely to couple to substrate via parasitic capacitance. Therefore, thicker upper-layer metal must be used to design inductors in order to reduce ohmic loss.
According to “A Ku-band CMOS low-noise amplifier” (IEEE Radio Freq. Integ. Tech., pp. 183-186, December 2005, K. L. Deng et al), a Ku-band low-noise amplifier designed by employing 0.18 μm CMOS process is disclosed. The architecture of this low-noise amplifier consists of two common-source amplifiers, and low-pass filter circuits are used, hence this low-noise amplifier has rather high power consumption.
According to “A 24 GHz 3.9 dB NF low-noise amplifier using 0.18 μm CMOS technology” (IEEE Microw. Wireless Comp. Lett., vol. 15, no. 7, pp. 448-450, July 2005, S. C. Shin et al), a 24 GHz low-noise amplifier by employing 0.18 μm CMOS process is disclosed, the architecture of this low-noise amplifier consists of two common-source amplifiers, and the bias network of the first stage is integrated with the input matching circuit in order to decrease the sensitivity to noise, hence the noise factor is low (NF=3.9 dB), and its power consumption is 14 mW at 1V power supply voltage.
In view of the above, it is a highly urgent issue in the industry to provide a low-noise amplifier, which has low voltage, low power consumption, and low production cost, thereby effectively solving the drawbacks of the prior arts as mentioned above.